Forgive me if this has been discussed but I think I picked up on something. When Tywin was talking to Tyrion, telling him about Robb's marriage to Jeyne, he comments that she is her mother's daughter. I took this to mean that the whole marriage was relatively schemed on the go, as such, and that Sybelle Westerling was in cahoots with Tywin. I don't mean everything was planned but I belive they co-operated when the opportunity arose to stuff up Robb's alliance with the Freys. My belief is furthered by the fact that Jaime observes that Sybelle was a schemer and had orchestrated a deal with the Lannisters for notable matches for her children. Also Sybelle tells Jaime that she had made sure Jeyne was not pregnant. Previously Jeyne had told Catelyn that Sybelle made her a fertility posset of herbs and such, which makes me think that she was preventing Jeyne from conceiving, as per her deal with Tywin.
I picked up on another thing I found interesting, I think the Magei that cursed Cersei was Jeyne's grandmother or great grandmother as Tywin tells Tyrion that Lord Westerling should never have married Sybelle Spicer as she was desended from some witch woman a Spicer had bought back from the east, which matches in with what Cersei's POVs tell us in aFfC. So, is it possible that Jeyne will be Cersei's downfall? She is still considered a queen by some and if her own grandmother was Cersei magei, it would fit neatly. Sorry for the rambling.
I picked up on another thing I found interesting, I think the Magei that cursed Cersei was Jeyne's grandmother or great grandmother as Tywin tells Tyrion that Lord Westerling should never have married Sybelle Spicer as she was desended from some witch woman a Spicer had bought back from the east, which matches in with what Cersei's POVs tell us in aFfC. So, is it possible that Jeyne will be Cersei's downfall? She is still considered a queen by some and if her own grandmother was Cersei magei, it would fit neatly. Sorry for the rambling.